1. Field of the Invention
The present invention relates to a device for adjusting the inclination of the light axis of headlamps of a motor vehicle.
2. Description of the Prior Art
The headlamps of a motor vehicle or car, for example, are needed to light ahead the car in such a way that the driver can drive the car without hindrance and that those who drive cars coming up cannot be dazzled by the light. The headlamps attached to the car in the course of car assembly are therefore aiming-adjusted to exactly direct their light axis so as to achieve easy driving but not to dazzle the drivers who operate cars coming up. The light axis of the headlamps change, however, depending upon the carrying conditions such as number of persons boarded and weight of cargo loaded. Namely, they are shifted upward when a heavy cargo is loaded on the back of the car but downward when it is loaded on the front of the car. It often happens, therefore, that driving of the car is made troublesome and that those who drive cars coming up are dazzled. Accordingly, the conventional headlamp for motor vehicles is provided with the device for levelling the headlamp so as to adjust (or correct) the inclination of the light axis of said headlamp to return to its aimed position, counterbalancing various changes of car condition.
In the case of the conventional device for adjusting the inclination of the light axis, however, the headlamp levelling means is independent of the aiming means. Upon attaching these means to the headlamp, therefore, the aiming means must be connected to the device for adjusting the inclination of the light axis of headlamp means of a different connector, thereby increasing the number of parts used and making their attachment to the headlamp complicated and the space which they occupy large.
The conventional devices for adjusting the inclination of the light axis of headlamp are grouped in construction to the type wherein the light axis is changed according to the amount of linear movement of a shaft driven by a motor and wherein the angle of the headlamp is detected by the operation of a switch which serves to detect the moved position of the shaft; and to the other type wherein both of a motor and a wire are used in such a way that the crank-connected wire is tensioned by the motor to change the angle of the headlamp in upward and downward directions. With these light axis adjusting devices in which the amount of linear movement of the shaft itself determines the range of inclination angle of the light axis, the amount of movement of the shaft is asked to be extremely small because the device must be small-sized, so high accuracy angle adjustment cannot be attained. In addition, the extent to which the device of this type can be small-sized is limeted. When it is sized as small as possible, the angle of the light axis and the light-axis-adjusted position cannot be detected with high accuracy. Further, a large operational loss is caused in the driver circuit for adjusting the inclination of the light axis.